Offspring sex and pregnancy outcome by length of gestation

BACKGROUND: It takes a higher number of male than female embryos to produce a live born infant. The unbalanced pregnancy survival by offspring sex may also be reflected in higher proportion of preterm male births, and in unbalanced sex distribution in certain pregnancy conditions, such as preeclampsia. METHODS: We used data from the Medical Birth Registry of Norway, a population-based registry that has recorded births since 1967. For this study, we used information on offspring sex and length of gestation that was available for 1691053 (92.8%) singleton births among a total of 1822982 births from 1967 to 1998. We estimated sex ratios and perinatal mortality by length of gestation, and assessed whether the ratio of offspring sex in preeclampsia varied by length of gestation. RESULTS: For preterm births, there was a strong male dominance. Within five categories of gestational age between 16 and 36 weeks, the male/female ratios were 2.48, 1.26, 1.28, 1.32, and 1.28. At weeks 37-39, the sex ratio was 1.17, but at weeks 40-42 the number of male and female births was practically identical (sex ratio 1.00). Over all, the male/female ratio was 1.06. Perinatal mortality was consistently higher in males across the whole range of gestational age; in total it was 21% (95% CI, 18-25%) higher in male offspring. In preeclampsia with preterm delivery (<37 weeks), the sex ratio was reversed: female offspring was substantially more common than males (sex ratio 0.87), but in preeclampsia with delivery at term (37-42 weeks), the proportion of males was higher (sex ratio 1.06) than for females. CONCLUSION: The sex differences by length of gestation and in preeclampsia may reflect that male embryos are subject to stronger intrauterine selection forces than females. Possibly, implantation may be the critical event, where offspring sex may be one of the factors that determine success.     

Ultrasound estimates of gestational age among perinatally demised: a population-based study

BACKGROUND: Correct estimation of gestational age may improve the quality of obstetric care. We hypothesize that significant differences between traditional and alternative estimates by ultrasound are evident among perinatal deaths. METHODS: Population-based case series with data linkage between autopsy records and The Medical Birth Registry of Norway, including perinatally demised singletons who were examined by autopsy and post-mortem radiography, having antenatal estimates of gestational age both by the calendar method, as calculated from the first day of the last menstrual period preceding the pregnancy (GAlmp), and by mid-second-trimester ultrasound (GAus), N = 380. The main outcome measure was the distribution of GAlmp and GAus within weight strata. RESULTS: Mean GAus was 1 week less than mean GAlmp (t-test, p < 0.001). The degree of apparent growth restriction manifest after death, as expressed by both birthweight and by post-mortem radiographic measurements, was fairly well correlated with the degree of downward adjustment of age by ultrasound in the early second trimester (Pearson's correlation, r = - 0.599, p < 0.001). The degree of discrepancy between the ultrasound and the calendar methods was associated both with placenta findings (Kruskal-Wallis test, chi2 = 20.95, p = 0.007) and with the main cause of death (Kruskal-Wallis test, chi2 = 27.65, p = 0.004). CONCLUSION: Among infants who died perinatally, gestational age seemed to be systematically downward adjusted by mid-second-trimester screening ultrasound, particularly among those who were the most growth retarded at the time of death.     

Grandparents' age and the risk of Down's syndrome in Norway

BACKGROUND: High maternal age is a well-recognized risk factor for Down's syndrome. There are also several studies of a possible effect of paternal age, but no consistent evidence of an association is found. Less is known about any effects of the age of grandparents. Objective. To assess whether maternal or paternal grandparents' age is associated with the risk of Down's syndrome. METHODS: We used logistic regression analyses with data from the Medical Birth Registry of Norway, adjusting for possible confounding factors. RESULTS: We found no evidence of an association with the risk of Down's syndrome either for a maternal grandmother's age (odds ratio 0.9, 95% confidence interval 0.6-1.5 per 10-year increase in grandmother's age) or for any of the other grandparents' age. CONCLUSIONS: High maternal age remains the only well-established age-related risk factor for Down's syndrome. There is little evidence that the increased risk represented by older mothers is passed on to offspring of her non-affected daughters.     

Maternal mortality in northern rural Tanzania: assessing the completeness of various information sources

BACKGROUND: To assess the completeness of various information sources and the subsequent estimates on maternal mortality. METHODS: Maternal deaths in the study area, rural northern Tanzania, in 1995 were identified from hospital records, health centers and dispensaries, registration by village leaders, follow up of an antenatal cohort, and a household survey. Data from some of these sources were also obtained in 1996. RESULTS: In 1995, 22 of a total of 26 maternal deaths were identified at the Haydom hospital. Three of the 15 deaths (20%) reported by the village leaders were not identified at any health facility. Four deaths were found in the antenatal cohort and one death in the household survey. Only two deaths were reported by the official statistics. Of the identified maternal deaths, 85% were found from health facility data. Including data from 1996, a total of 45 maternal deaths were identified; 13 of which were direct and 32 indirect obstetric deaths. The 1995 estimated maternal mortality ratio, based on reports from the multiple source registrations, was 382 (95% confidence interval 250-560) per 100 000 live births. The antenatal cohort yielded an estimate of 322 (95% confidence interval 160-580). The ratio based on official figures for 1995 and 1996 combined was 123 (95% confidence interval 70-200). CONCLUSIONS: Even a high quality routine registration of maternal deaths will miss a small proportion of cases. Investing in better registration of direct and indirect obstetric deaths will give better insight into this important health problem. Estimates based on official reports showed substantial underreporting.     

A medical birth registry at Kilimanjaro Christian Medical Centre

OBJECTIVE: To establish a medical birth registry intended to serve clinical, administrative and research purposes. METHODS: Starting in July 2000, every birth at Kilimanjaro Christian Medical Centre (KCMC) in Moshi, Tanzania has been recorded in a separate database. The information is obtained through personal interviews with each mother, conducted by specially trained midwives, and supplied with data from the medical records. A secretary enters the data into the electronic file. Data are collected about the mother and father: education, occupation and living conditions, mother's health before and during present pregnancy, expected date of delivery, smoking and drinking (alcohol) habits, use of drugs, plus HIV and syphilis status (if known). This is followed by particulars on the delivery: spontaneous or induced, and complications; the child or children: weight, height and Apgar score, malformations and other diagnoses. Mode of birth: spontaneous or operative intervention. If perinatal death: when? Transfer to intensive neonatal unit? The mother's reproductive history (births, miscarriages, ectopic pregnancies) is also recorded, with outcomes. RESULTS: We describe the process based on more than six years' experience, including obstacles and how they were overcome. The registry serves as a monitoring tool, with a set of key activities and events being issued monthly, indicating changes and trends in, e.g., bleeding complications, caesarean section rates and perinatal mortality, as early warning signs. Monthly reports on key issues are presented. Confidentiality and data protection are key issues. Day-to-day recording of births is vulnerable to personnel shortage, whether from disease or holidays. CONCLUSIONS: Validation and quality checks leave the overall impression that the database is largely accurate and credible. There are plenty of opportunities for research. Clinicians and epidemiologists will profit from using the database to test hypotheses and clarify problem issues, to the ultimate benefit of labouring women and their children.     

The epidemic of SIDS in Norway 1967-93: changing effects of risk factors

Time trends on the association of maternal age, birth order, and marital status with the risk of sudden infant death syndrome (SIDS) and non-SIDS deaths in Norway were analysed: 2356 postperinatal SIDS deaths and 4069 postperinatal non-SIDS deaths were ascertained during 1967-93. The SIDS incidence was 1.25 per 1000 in 1967, reached a peak of 2.69 in 1988, and fell to 1.22 in 1990 after the initiation of an intervention programme to avoid prone sleeping. In the entire period, young maternal age, high birth order, and unmarried motherhood were associated with SIDS. The adverse effects of young maternal age and high birth order increased continuously with time. From 1967-71 to 1990-93, the relative risk for maternal age < 20 years v maternal age 25-29 changed from 2.5 (95% confidence interval 2.0 to 3.2) to 7.0 (95% CI 4.2 to 11.9) (p < 0.0001), and for birth order 4+ nu birth order 1 from 3.2 (95% CI 2.5 to 4.2) to 14.4 (95% CI 8.3 to 24.9) (p < 0.0001). Effects on non-SIDS deaths were far weaker and no secular trends were observed. The strong association of young maternal age, high birth order, and marital status in SIDS, but not in non-SIDS, provides evidence that SIDS is an epidemiological entity. The increasing effects of young maternal age and high birth order, which continued after the sudden drop in the SIDS rate in 1990, suggest that further efforts to prevent SIDS should be aimed particularly at identifying causal mechanisms in high risk groups.